Prestressing fixture to eliminate automotive p.s.i.r. door-chute vibration weld visibility

ABSTRACT

An automotive interior component including an airbag chute having at least one weld bar, and a pre-stressed instrument panel having a substrate layer for bonding to the weld bar. The pre-stressing provides tensile stress at weld bar bonding areas to reduce any deformation visible on an exposed surface of the instrument panel.

RELATED APPLICATIONS

This application claims the benefit of priority to ProvisionalApplication Ser. No. 60/873,274, filed Dec. 7, 2006, incorporated byreference in its entirety.

BACKGROUND OF INVENTION

a. Field of Invention

The invention relates generally to automotive instrument panels, anapparatus for and method of manufacture thereof, and, more particularly,to an apparatus for and method of manufacturing automotive instrumentpanels and other automotive components which eliminates distortion inthe area of vibration welded Passenger Side Inflatable Restraint (PSIR)chutes and other vibration welded components.

b. Description of Related Art

Automobiles are commonly equipped with airbags for reducing driver andpassenger injuries in the case of an accident. Automobile airbags aregenerally located in areas where a driver or passenger would potentiallycontact an automobile interior in the event of an accident. Airbags canreduce injuries by providing a substantially non-solid surface for thedriver or passenger to contact, as opposed to the generally solidsurfaces of the automotive interior. Although the functionality of theairbag is greatly valued, the visual appeal of the instrument panel, andinvisibility of the airbag system are also of value to automobilemanufacturers and consumers alike.

In order to install an airbag, the airbag is generally folded into amodule that is installed into or behind an automotive interiorcomponent. The module housing a passenger-side airbag is generallyinstalled on the underside of an instrument panel, within a PSIR chuteprotruding behind the instrument panel. The instrument panel willgenerally have a pre-weakened area, allowing an airbag to releasetherethrough. A PSIR chute will be bonded to the instrument panel, andwill generally include doors that line up with the pre-weakened area ofthe instrument panel.

A known method for attaching a PSIR chute to an instrument panelincludes vibration welding the PSIR chute to the instrument panel.Vibration welding joins components by “rubbing” them together, creatingheat through the friction, melting the connection points, andapplying/holding pressure until the components cool together, therebywelding the components at the contact points. During the coolingprocess, there is known to be shrinkage/deformation of materials.Namely, during the known vibration welding of an instrument panel andPSIR chute, there is a visible deflection of the instrument panel at theconnection points between the components caused by uneven shrinkageduring the cooling process.

It would therefore be of benefit to provide an apparatus and method ofmanufacturing automotive instrument panels and other structuresincluding air bags and other vibration welded components to include aflat (or predetermined contoured) appearance in the area of thevibration welds.

SUMMARY OF THE INVENTION

The present invention overcomes the drawbacks and deficiencies of knownmethods and apparatus for attaching a PSIR chute to an instrument panelby providing an automotive interior component including an airbag chutehaving one or more weld bars and a pre-stressed instrument panel havinga substrate layer for bonding to the weld bar. For the instrument panel,tensile stress at weld bar bonding areas reduces any deformation visibleon an exposed surface of the pre-stressed instrument panel, by matchingthe “B” surface stretch under the tensile stress of local bending to theexpected shrink of the melted layer.

For the automotive interior component described above, the weld bars ofthe airbag chute may be vibration welded to the “B” side of the plasticinstrument panel. The interior component may further include a coverlayer bonded to the substrate layer. The cover layer may be made ofpolyvinyl chloride or ThermoPlastic Olefin, and in an exemplaryembodiment, may have a thickness of 0.4-1.0 mm. The interior componentmay further include a cover layer and an intermediate foam layer bondedto the substrate layer. The foam layer may be made of polypropylene, andin an exemplary embodiment, may have a thickness of 0.5-3.0 mm. Thesubstrate layer may include thermoplastic polymers, and in an exemplaryembodiment, may have a thickness of 2.0-4.0 mm.

The invention also provides an apparatus for pre-stressing an automotiveinstrument panel for eliminating distortion in an area of vibrationwelded airbag chutes. The apparatus may include a weld fixture includinga plurality of convex pre-stressors disposable against an instrumentpanel for creating compression in an area of contact with an instrumentpanel and creating tension in a surface opposite the contact area uponapplication of vacuum to draw the instrument panel toward the weldfixture. The weld fixture may be disposable against a cover layer of theinstrument panel and creates tension in a substrate layer of theinstrument panel, with the substrate layer being disposed adjacent anopposite face of the cover layer with or without an intermediate foamlayer being disposed between the cover and substrate layers.

The invention yet further provides a method of manufacturing anautomotive instrument panel for eliminating distortion in an area ofvibration welded air bags. The method may include providing a weldfixture including a plurality of pre-stressor protrusions, and placingthe pre-stressor protrusions against an instrument panel. The method mayalso include generating a force to press the weld fixture against theinstrument panel to create compression in an area of contact of the weldfixture with the instrument panel and tension in a surface opposite thecontact area, and vibration welding an air bag chute to the instrumentpanel such that a weld bar of the air bag chute is welded to the surfaceplaced in tension.

For the method described above, the instrument panel may also include asubstrate layer, a foam layer attached to the substrate layer, and acover layer attached to the foam layer. For the method described above,placing the pre-stressor protrusions includes placing the pre-stressorprotrusions against the cover layer of the instrument panel, andvibration welding further includes vibration welding an air bag chute tothe substrate layer.

Additional features, advantages, and embodiments of the invention may beset forth or become apparent from consideration of the followingdetailed description, drawings, and claims. Moreover, it is to beunderstood that both the foregoing summary of the invention and thefollowing detailed description are exemplary and intended to provideexplanation without limiting the scope of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate preferred embodiments of theinvention and together with the detail description serve to explain theprinciples of the invention. In the drawings:

FIG. 1 is a view illustrative of a related art instrument panel and PSIRchute, prior to vibration welding of the PSIR chute to the instrumentpanel;

FIG. 2A is a view illustrative of the related art instrument panelconstruction of FIG. 1, illustrating various distortions in theinstrument panel visible surface due to vibration welding of the PSIRchute;

FIG. 2B is an enlarged view of the related art instrument panelconstruction of FIG. 1, illustrating distortion in the area of thecenter score weakening line;

FIG. 3 is a view illustrative of a modified weld fixture surface forpre-stressing of the instrument panel according to the presentinvention;

FIG. 4 is a view illustrating pre-stressing of the instrument panelaccording to the present invention;

FIG. 5 is a view illustrating vibration welded attachment of a PSIRchute;

FIG. 6A is a view illustrative of a pre-stress layered instrument panelaccording to the present invention, illustrating a PSIR chute vibrationwelded thereon; and

FIG. 6B is an enlarged view of the pre-stressed layered instrument panelof FIG. 6A for absorbing any distortions from vibration welding of thePSIR chute.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings wherein like reference numerals designatecorresponding parts throughout the several views, FIGS. 1-2B are viewsillustrative of a related art instrument panel construction, FIGS. 3-5are views illustrative of an instrument panel construction foreliminating distortion in the area of vibration welded PSIR chutesaccording to the present invention, and FIGS. 6A and 6B are viewsillustrative of a pre-stressed layered instrument panel according to thepresent invention.

Referring to FIG. 1, in “hard hidden” constructions, a PSIR Chute 10 isoften vibration welded to the underside of prior art instrument panel12. As briefly discussed above, the technique of vibration weldinggenerally involves the physical movement PSIR Chute 10 having weld bars14 relative to prior art instrument panel 12, with weld bars 14 beingmoved horizontally relative to instrument panel 12 under pressure. Thisphysical movement creates heat which melts contact area 16 of prior artinstrument panel 12, and thus allows weld bars 14 to be welded to priorart instrument panel 12 upon cooling of areas 16 when the relativemovement is stopped.

Referring to FIGS. 2A and 2B, upon cooling, the thermal shrinkage incontact areas 16 causes compression in areas 16 and tension in theopposite visible areas 18 of the prior art instrument panel. Further,the thermal shrinkage in contact areas 16 also causes bending in area 20of center score line 22.

Referring to FIG. 3, the present invention generally provides aninstrument panel construction technique using a modified weld fixture 32(illustrated as a lower weld fixture in FIG. 3) including a plurality ofspaced convex pre-stressors 34. In the embodiment illustrated, eachpre-stressor 34 may be a smooth convex curved shape, however protrusionsof various configurations may be used to transfer the desired force tothe instrument panel. Referring to FIGS. 3-5, each pre-stressor 34 maybe disposed adjacent visible surface 36 of instrument panel 38 and isfurther disposed opposite weld bars 14. Referring to FIG. 3, eachpre-stressor 34 may include a predetermined height to bend instrumentpanel 38 such that the tension induced stretch on the back surface 40matches the expected. weld shrink to thus eliminate distortion in thearea of weld bars 14. Where the technique is used on a pre-stressedlayered instrument panel (as discussed below), pre-stressors 34 may bedisposed adjacent to a cover layer and tension may be on substrate layer30 (refer to FIG. 6B). Modified weld fixture 32 may further include aplurality of holes (not shown) for creating compression in areas 42 andtension in areas 44 of instrument panel 38 upon the application of avacuum to draw instrument panel 38 toward fixture 32. A vacuum seal (notshown) may be provided around instrument panel 38 for creating a vacuumas discussed above. Although a vacuum force is described herein, thoseskilled in the art would appreciate the application of similar forces tothe modified weld fixture 32 and instrument panel 38. Namely, instead ofusing vacuum to draw instrument panel 38 toward weld fixture 32, weldfixture 32 (and another upper weld fixture (not shown) for holding theair bag chute) may be simply pressed against instrument panel 38 (andair bag chute 46) to thus create the aforementioned compressed/tensionedareas.

The manufacturing method of instrument panel 38 according to the presentinvention will now be described in detail with reference to FIGS. 3-5.As shown in FIG. 3 and briefly discussed above, instrument panel 38 maybe disposed relative to modified weld fixture 32, with visible surface36 of instrument panel 38, or the surface of substrate layer 30 adjacentfoam layer 28 of pre-stressed layered instrument panel 24 as shown inFIG. 6B (see discussion below), being disposed in contact withpre-stressors 34 of weld fixture 32. The instrument panels may belaterally aligned relative to weld fixture 32 such that eachpre-stressor 34 is disposed opposite the weld bars 14. A vacuum may thenbe created to draw instrument panel 38 (or 24 of FIGS. 6A and 6B)towards weld fixture 32 via the holes (not shown) in weld fixture 32. Inan exemplary embodiment of the present invention, the vacuum may begenerated at 13 psi, with the instrument panel being maintained at roomtemperature. Further, in an exemplary embodiment, weld fixture 32 (andthe weld fixture for air bag chute 46) may be machined aluminum andinclude a thin (i.e. ⅓ min) urethane layer to prevent scratching ordamage to the grain of instrument panel 38 (or 24 of FIGS. 6A and 6B).

Referring to FIG. 4, after vacuum application, instrument panel 38 (or24 of FIGS. 6A and 6B) may include compression in areas 42 and tensionin areas 44 to thus create an uneven instrument panel visible surfaceprior to vibration welding of air hag chute 46.

Referring next to FIG. 5, with weld fixture 32 held in place relative toinstrument panel 38 (or 24 of FIGS. 6A and 6B), air bag chute 46including weld bars 14 (and another upper weld fixture (not shown) forholding the air bag chute) may be vibration welded to instrument panel38. Upon cooling of weld areas 44, the initial stretch due to tension inareas 44 (see FIG. 4) is matched by the thermal shrinkage created bycooling of weld areas 44 to thus create a horizontal (or otherwisepredetermined contoured) instrument panel visible surface 36 withoutdistortion.

Referring now to FIGS. 6A and 6B, as briefly discussed above, in analternative embodiment of the instrument panel, PSIR Chute 10 havingweld bars 14 may be vibration welded to pre-stressed layered instrumentpanel 24 at contact areas 16. As shown in FIG. 6B, pre-stressed layeredinstrument panel 24 may include cover layer 26, which may be about0.4-1.0 mm of polyvinyl chloride, ThermoPlastic Olefin, a blend ofpolypropylene, polyethylene and/or rubber, or like thermoplasticpolymers. Panel 24 may further include a foam layer 28 includingpolypropylene foam or like material of about 0.5-3.0 mm thickness, and asubstrate layer of 30 of 2.0-4.0 mm thick ThermoPlastic Olefin or likematerial. Substrate layer 30 may be formed by an injection moldingprocess. Cover layer 26 and foam layer 28 may be vacuum wrapped over thesubstrate layer 30. Weld bars 14 may be vibration molded at contactareas 16 to substrate layer 30.

Whereas visible distortion in areas 18 and center area 20 appear in therelated art (see FIGS. 2A and 2B), distortions are not visible throughthe pre-stressed layered instrument panel 24, as the pros-stressedcombination of substrate layer 30, foam layer 28, and cover layer 26 actto absorb any distortion caused by vibration welding. Whereas theembodiment of pre-stressed layered instrument panel 24 has beendescribed as being formed by placement of convex pre-stressors 34adjacent the surface of substrate layer 30 adjacent foam layer 28, it isconceivable that pre-stressors 34 may be placed on the exposed surfaceof cover layer 26.

Those skilled in the art would readily appreciate in view of thisdisclosure that various modifications may be made to the instrumentpanel construction technique described above, without departing from thescope of the present invention. For example, while instrument panelconstruction technique has generally been discussed in conjunction withvibration welded assembly of air bags, this technique may be readilyused with other vibration welded components for eliminating distortionin the area of the vibration weld. Further, while the use ofpre-stressors 34 has been discussed for eliminating distortion in aninstrument panel, pre-stressors 34 may be also used as needed to createa predetermined contoured appearance in the area of an instrument panelor other structures for providing a desirable contoured aestheticappearance.

Although particular embodiments of the invention have been described indetail herein with reference to the accompanying drawings, it is to beunderstood that the invention is not limited to those particularembodiments, and that various changes and modifications may be effectedtherein by one skilled in the art without departing from the scope orspirit of the invention as defined in the appended claims.

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 10. (canceled) 11.An apparatus for manufacturing a pre-stressed automotive instrumentpanel for eliminating distortion in an area of vibration welded airbagchutes, said apparatus comprising: a weld fixture including a pluralityof convex pre-stressors disposable against an instrument panel forcreating compression in an area of contact with an instrument panel andcreating tension in a surface opposite the contact area upon applicationof vacuum to draw the instrument panel toward the weld fixture.
 12. Anapparatus according to claim 11, wherein the weld fixture is disposableagainst a cover layer of the instrument panel and creates tension in asubstrate layer of the instrument panel, the substrate layer beingdisposed adjacent an opposite face of the cover layer with or without anintermediate foam layer being disposed between the cover and substratelayers.
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